Low and intermediate temperature metal supported solid oxide fuel cell operating with practical fuels

固体氧化物燃料电池（SOFC）是一种具有较高电效率的高温燃料电池，可用于热电联产。由于操作温度高，电催化剂通常为镍，镍也是一种活性重整催化剂。因此，sofc具有燃料灵活性，可以使用天然气、酒精、液化石油气、合成气（即气化或重整的产品，通常主要由CO和H2组成）等。最先进的sofc在800-1000C范围内工作。由于这种高温，材料仅限于陶瓷材料，从而使SOFC昂贵且易碎。为了降低成本，提高耐用性和坚固性，正在努力将工作温度降低到750℃以下，以便金属可以用作支撑；这种设计被称为金属支撑电池（MSC）。如果需要燃料重整，电池温度不应过低；对于MSC，温度在625-700C（中间温度）左右是理想的。如果重整不是问题（例如H2或最终合成气），那么电池温度可能会下降到500-600℃范围内（低温）。

Solid oxide fuel cells (SOFC) are high temperature fuel cells that can achieve high electrical efficiency and be used in combined heat and power. Because of the high operating temperatures, the electro-catalyst is usually nickel, which is also an active reforming catalyst. SOFCs are, therefore, fuel-flexible and can run with natural gas, alcohol, LPG, syngas (i.e. products from gasification or reforming, usually composed primarily of CO and H2), etc. State-of-the-art SOFCs operate in the range 800-1000C. Because of such high temperatures, materials are limited to ceramic ones, thus making SOFC expensive and brittle. In order to reduce cost and improve durability and ruggedness, efforts are being made to reduce the operating temperature below 750C so that metals could be used as support; such design is called metal-supported cell (MSC). If fuel reforming is desired, the cell temperature should not be too low; for MSC, temperatures around 625-700C (Intermediate Temperature) would be ideal. If reforming is not an issue (e.g. with H2 or eventually syngas), then the cell temperature could drop in the 500-600C range (Low Temperature). An important obstacle against the direct use of hydrocarbons in SOFC is the propensity for carbon to deposit on the Ni electro-catalyst (also referred to as coking). In addition, most of the practical fuels contain sulphur, which is also a problem in conventional SOFC anodes. MSC actually offers the possibility to tackle both the coking and sulphur issues. Design of carbon and sulphur resistant MSC is the primary objective of the proposed research. The first point is that in MSC, the anode is usually comprised of Ni and some ceria-based materials, such as samaria-doped ceria (SDC). Ceria is known to increase both coking and sulphur resistance. Ceria is also active toward oxidation reactions. The second point is that in MSC, the anode can be designed so that part of the metal support becomes the primary electronic conductor of the anode; this function is usually that of Ni in non-metal supported SOFC cells. The implication is that the Ni content can be then considerably reduced. In the proposed work we are aiming at making MSC anodes with highly dispersed and non-coarsening Ni nanoparticles. We will fabricate MSC button cells following two MSC fabrication methods: 1) Ni-SDC infiltrated in YSZ backbone with YSZ electrolyte and 2) Ni-SDC co-firing with SDC electrolyte. The MSC button cells will then be tested under various conditions of temperatures and feed compositions in an electrochemical test station to assess their performance, stability, and resistance to coking and sulphur. In addition to the experimental work, we will also develop elementary-based reaction single cell simulations to serve as a design tool to optimize the anode. These simulations will be developed in Comsol Multiphysics and will be able, among others, to predict carbon deposition. The kinetics of charge transfer reactions on Ni-SDC is very important in this model, but they are currently not known. An in-depth kinetic study using pattern anode, for which we have developed some expertise, will also be carried out. Additional kinetic studies will also be pursued for chemical reactions on Ni-SDC, such as water-gas shift and CO disproportionation. The simulation will be validated using the MSC electrochemical tests over a wide range of operating conditions. The validated model will then be used to study the effect of operating and structural parameters, such as anode thickness and porosity, temperature or feed composition, in order to evaluate conditions that lead to stable operation using methane and syngas fuels. Whenever possible, those conditions will be checked experimentally.